I'll take the liberty to say yes, that is what they mean, and that is their point: there is no way to detect whether those keys are available, so the best we can do is guess.
And yes, I might actually need to know whether there is a physical keyboard or not. For example, do I auto-focus the input field? For devices with OSKs, the keyboard will pop up right away and obscure most of the site on mobile. For devices where the OSK won't pop up, I want the focus to land there immediately for usability.
A time entry input is a good example: on the PC you can accept valid [0123456789:.APMapm] characters as the user types, and have the HTML page do something sensible and show something sensible. On Android you either have an ugly time picker (they are all ugly!) or use hideous workarounds to try and detect keypresses.
Android and iOS have `inputmode=` but it is very restricted and there are wierd and sometimes incompatible differences between browsers or browser versions or OS versions. Custom data entry (e.g. time, date ranges, etc) is super ugly in HTML.
I have found many browser version and device specific bugs with virtual keyboards or PC keyboard entry that cannot be "feature detected" (browser version must be sniffed).